Shielded window construction



1967 w. F. BAKKER ETAL 3,305,623

SHIELDED WINDOW CONSTRUCTION Filed Oct. 19, 1964 l l Ill/III!!! I P wF MWM? i 3 Jo Q J W M y B a 3,305,623 SHIELDED WINDOW CONSTRUCTION WillemF. Bakker, Clark, Arthur J. Johnson, Newark, and Joseph P. Kosiarski,Freehold, N.J., assignors to Metex Corporation, a corporation ofDelaware Filed on. 19, 1964, Ser. No. 404,801 6 Claims. (Cl. 17435) Thisinvention relates to shielded observation windows or similar devices forelectrical or electronic devices.

At present the prevention of radio frequency leakage through relativelylarge openings which require an undistorted view of some form of visualread out, is accomplished by means of a coated glass commonly calledconductive glass. Such material affords poor shielding effectivenessagainst radio frequency loss; the glass is heavy and relatively high incost and diffic-ulty is encountered in making proper contact between theconductive glass and the surrounding enclosure frame work.

It is an object of the present invention to provide a construction whichwill eliminate the above objections and other objections arising fromthe use of the conductive glass, and the present invention contemplatesthe provision of a window which employs a pair of overlying panes oftransparent plastic material such as Plexiglas between which issandwiched a layer of foraminous metallic mesh that extends co-planarwith the panes, the edges of the plastic panes and the edges of themetallic mesh being enclosed in a metallic mounting frame or rim.

In numerous types of electronic equipment which is totally enclosed orconfined in shielded boxes, it is frequently necessary or at leastdesirable that some means be provided to observe certain instruments,the functioning of parts of the apparatus or other features having abearing on the proper operation of the equipment.

It is accordingly, one of the objects of the invention to provide anobservation window for apparatus of this character, which can be made inalmost any shape and size to suit special equipment, and which will beprovided with shielding material to suppress or exclude radio frequencyinterference.

It is another object of the invention to provide means for attaching theobservation window to the equipmentcontaining enclosure and in such amanner that no objectionable radio frequency leaks will occur around theperiphery of the observation panel.

With these and other objects to be hereinafter set forth in view, wehave devised the arrangement of parts to be described and moreparticularly pointed out in the claims appended hereto.

In the accompanying drawing, wherein an illustrative embodiment of theinvention is disclosed,

FIG. 1 is a perspective view, with some parts fragmentarily shown, of ashielded observation window constructed according to the invention;

FIG. 2 is a transverse sectional view, taken substantially on the line2-2 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a face view of a part of the metallic knit mesh and a part ofthe metallic binding strip applied thereto; and

FIG. 4 shows an alternate form of metallic mesh.

Referring to the drawing, 1 and 2 respectively indicate a pair of sheetsor panes composed of a transparent plastic material, such as Plexiglasor another material of similar characteristics. Sandwiched between thesheets or panes 1 and 2 and lying co-planar therewith, is a layer 3 offoraminous conductive material, such as metallic mesh. Such material maybe composed of wire in the knitted form shown in FIG. 3 or it might beof the woven Wire type shown in FIG. 4 or of some other known wire mesh.

Such metallic shielding material while in the form of United StatesPatent 3,305,623 Patented Feb. 21, 1967 I CC an independent layerdisposed between the Plexiglas panes glas or other transparent plastic.

The layer 3 of shielding material, has its peripheral edge enclosed in abinding consisting of a channel strip 5 of metal, such as stainlesssteel foil, and to which the mesh 3 or 4 is spot welded as shown at 6,thereby providing a metallic enclosing rim or frame for the metal mesh.Both the metallic mesh, framed as above described, and the Plexiglassheets or panes 1 and 2 are confined in a surrounding frame 7 composedof metal or one which is both conductive and compressively resilient sothat it acts gasket-like when secured around an opening in a metallicenclosure as shown in FIG. 2.

The inner edge of the frame 7 is properly grooved, as shown at 9 for thereception of the edges of the Plexiglas panes and also grooved as shownat 10 to snugly receive the binding 5 that extends around the edges ofthe metal mesh 3, 4.

The result of the structure described is a shielded window which is ofsturdy construction; one which provides for complete visibility and onewhich is very effective to prevent radio frequency leakage. The windowconstructed as described, is attached over an opening in an enclosure bymeans of the bolts 11 or equivalent fastening means which pass throughthe frame 7 and through the marginal edge area defining the opening inthe enclosure 8. The frame 7, being to a certain degree compressible,serves as a gasket against the face of the enclosure 8 and establishesgood contact between the metallic mesh insert and the body of theenclosure.

While we have herein shown the shielding insert and window as beingsubstantially rectangular in shape, it will be understood that it may bemade in various other shapes according to the shape of the opening overwhich it is fitted. Also while we have suggested that the panes 1 and 2shall be of a plastic material such as Plexiglas, these panes can, ifdesired, be composed of glass.

The wire mesh may be replaced with a perforated metal element,photo-etched foil and/or a honeycomb construction with results which areimproved over those of the prior art. In addition, a plurality of layersof mesh or the like may be used, as for example, a multiple layersandwich having a layer of Plexiglas, then mesh, then a second Plexiglaslayer, then a second mesh, completed by a third layer of Plexiglas.

Having thus described the invention, it is obvious that the same is notto be restricted thereto, but is broad enough to cover all structurescoming within the scope of the annexed claims.

What we claim is:

1. A shielded window for electronic apparatus comprising an enclosurehaving an opening, a window fitted thereover and closing said opening,said window including a resilient and conductive frame, a pair oftransparent panes mounted in said frame, a layer of metallic foraminousmesh confined between the panes, with the edges of the mesh disposed inthe frame and in contact therewith, and wherein the edges of the metalmesh are enclosed in a metallic binding strip and said strip is fittedwithin and in contact with the resilient and conductive frame.

2. A shielded window comprising an enclosure having an opening, a windowfitted thereover and closing said opening, said wind-ow including aresilient and conductive frame, a pair of transparent panes mounted insaid frame, a layer of metallc foraminous mesh confined between thepanes, with the edges of the mesh disposed in the frame and in contacttherewith, and wherein grooves are provided in the inside edge of theframe receiving the panes and the metal mesh layer located between them.

3. A shielded window as provided for in claim 1, wherein the metal meshis composed of wire in knitted form having its edge contained in abinding strip of metal and said strip is fitted in the frame.

4. A shielded window as provided in claim 1, and wherein the metal meshis composed of wire in woven form and has its edge enclosed in andWelded to a metallic binding strip which is enclosed in the frame.

5-. A shielded window'for a metal enclosure for electronicequipment'comprising a substantially flat layer of foraminous metal, abinding strip around the edges thereof and gripping both faces of saidlayer, at least one sheet of transparent plastic material contacting aface of said layer, a conductive frame surrounding the edge of saidlayer, sheet and strip, and in contact with said sheet and strip, andmeans attached to said frame for anchoring said shielded window into anopening in said enclosure.

References Cited by the Examiner UNITED STATES PATENTS 2/ 1947 Naumann317-2 l/l960 Hahn.

LEWIS H. MYERS, Primary Examiner.

D. L., CLAY, Assistant Examiner.

5. A SHIELDED WINDOW FOR A METAL ENCLOSURE FOR ELECTRONIC EQUIPMENTCOMPRISING A SUBSTANTIALLY FLAT LAYER OF FORAMINOUS METAL, A BINDINGSTRIP AROUND THE EDGES THEREOF AND GRIPPING BOTH FACES OF SAID LAYER, ATLEAST ONE SHEET OF TRANSPARENT PLASTIC MATERIAL CONTACTING A FACE OFSAID LAYER, A CONDUCTIVE FRAME SURROUNDING THE EDGE OF SAID LAYER, SHEETAND STRIP, AND IN CONTACT WITH SAID SHEET AND STRIP, AND MEANS ATTACHEDTO SAID FRAME FOR ANCHORING SAID SHIELDED WINDOW INTO AN OPENING IN SAIDENCLOSURE.